Optimus takes out the key to the clamp, putting a hand on Starscream's shoulder just to ensure he doesn't do anything weird once he's taken the clamp off. Having Starscream mess with him again is really not what he needs right now.

He's honestly not sure if he wants to bother following through with that thought, based on Starscream's reaction. It's hard to imagine, from a strictly Optimus perspective, how anyone could be surprised by what had happened at all. The fact he had been, though, still stings. And though it is a futile thought, part of him wishes that Starscream was emotionally capable of feeling regret for it.

"I had considered you a friend, at a point during this. I was proven wrong."

The clamp clicks open, freeing Starscream's wings.